Currently, we have initiated an international collaborative trial that evaluates the role of letrozole in the primary maintenance setting called maintenance therapy with aromatase inhibitor in epithelial ovarian cancer; we are conducting a randomized, double-blinded, placebo-controlled, multi-center phase III trial (ENGOT-ov54/Swiss-GO-2/MATAO), ClinicalTrials.gov, accessed on 26 January 2020 (Identifier: NCT04111978). The gene discussed is CYP19A1; the disease is ovarian carcinoma.